Low clutch pedal engagement

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#1
Make
Jeep
Model
Wrangler
Year
1990
Miles
175000
Engine
4.2
1990 Wrangler with AX15 transmission. The transmission had a mild grind that could be felt mildly during shift. Grind into reverse almost every time. It's currently at a reputable transmission shop and they are running out of ideas. The pedal engages close to the floor. They have replaced the master 3x now and it just doesn't seem to want to pressurize. The clutch, slave and pilot were also replaced. They just went into the internals today and said everything looked great inside with the exception that the shifter bushing needed replacing. Any ideas on how to get the master up to pressure?
 

grcauto

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#2
They need to measure the travel. If it's short there's either air in the system or the master is bad.
 
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#3
Travel of what? Pedal or slave engagement? They have replaced the master 3x... Maybe 4. I haven't talked to them today. But all the new masters act exactly the same way. The pedal just feels really easy to push in after bleeding and the clutch engagement is maybe an inch off the floor.
 

bp042665

hunting nut
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#4
ok have they checked the clutch it self they do have transmission out good time to check it could have a weak pressure cover and that will cause this
 

billr

wrench
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#5
Check the end-play on the crank; excessive movement of the crank would subtract from the available "travel". It is not a likely problem, but I have run into similar with a crank that had about 1/8" end-play (and the engine ran fine).

Off topic, but I had to battle a bit to get it covered under a used-car warranty. Clutches were not covered by the warranty, only "oil-wetted" parts. Yeah, I had to convince them that the root problem was the crank and that the crank was one of the prime oil-wetted pieces.
 
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#6
ok have they checked the clutch it self they do have transmission out good time to check it could have a weak pressure cover and that will cause this
They replaced clutch already. The flywheel looked to be perfect but they are shimming it out now. Hoping to take up the slack with that.
 
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#8
Did the old clutch engage in this way?

Yep. Since I've owned it the clutch had had low engagement and the grind. The previous owner and the owner before him bubble gummed many things. I've been fixing everything on it. The housing electrical nuts on the power wire to the HEI was the best.
 
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#9
A hydraulic clutch is just like front wheel disc brakes, only advantage of it is both are inherently self adjustable, mechanical clutches had to be continuously self adjustable.

Really no mechanical advantage of a hydraulic clutch, the movement of the pressure plate and the clutch pedal is the same.

The disadvantage of a hydraulic clutch is they are a PITA to repair in particular with problems in the slave cylinder, on FWD vehicles, the entire transmission has to be removed.

Dealing with the same hygroscopic Dot 3 or 4 brake fluid that gums up, uses those cone like seals that can leak passing fluid backwards letting you push your pedal to the floor. GM got so sloppy with these things, using the same fluid reservoir for both the brakes and the clutch, if you lost fluid, no brakes, and couldn't even downshift to help you stop, really very poor.

You don't mention replacing the slave cylinder, kind of retarded to replace the master cylinder three time with no mention of the salve cylinder, that wears out quicker than the master, near the clutch depending on the driver, clutch can get red hot.

Another factor just like brakes, the slave has to be bled, bleeder is typically part of the hose near the slave cylinder, never had the pleasure of working on a Jeep, but the principles are all the same. Air in the line will let that pedal go to the floor without disengaging the pressure plate.

Ha, invented a whole new cuss word vocabulary working on hydraulic clutches in FWD vehicles.
 
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#10
A hydraulic clutch is just like front wheel disc brakes, only advantage of it is both are inherently self adjustable, mechanical clutches had to be continuously self adjustable.

Really no mechanical advantage of a hydraulic clutch, the movement of the pressure plate and the clutch pedal is the same.

The disadvantage of a hydraulic clutch is they are a PITA to repair in particular with problems in the slave cylinder, on FWD vehicles, the entire transmission has to be removed.

Dealing with the same hygroscopic Dot 3 or 4 brake fluid that gums up, uses those cone like seals that can leak passing fluid backwards letting you push your pedal to the floor. GM got so sloppy with these things, using the same fluid reservoir for both the brakes and the clutch, if you lost fluid, no brakes, and couldn't even downshift to help you stop, really very poor.

You don't mention replacing the slave cylinder, kind of retarded to replace the master cylinder three time with no mention of the salve cylinder, that wears out quicker than the master, near the clutch depending on the driver, clutch can get red hot.

Another factor just like brakes, the slave has to be bled, bleeder is typically part of the hose near the slave cylinder, never had the pleasure of working on a Jeep, but the principles are all the same. Air in the line will let that pedal go to the floor without disengaging the pressure plate.

Ha, invented a whole new cuss word vocabulary working on hydraulic clutches in FWD vehicles.
Original post states slave was replaced. At this time everything inside the bell housing is new. One thing that was found today is the alignment dowels were missing. Hopefully between those being put in and the flywheel being shimmed out a bit it'll be fixed finally.
 
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#11
Update: Working correctly now. Shifter bushing replaced, flywheel shimmed, and the alignment dowels installed. Along with everything else the transmission is now working correctly.
 
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#13
Front dif axle seals. Carb rebuild. All door seals. Interior door handles. New bumpers. And whatever else I find that needs to be replaced while doing those things. The way this thing has been, something will break.